Longer, surely? (Though I don't have any evidence I can point to).

It's in-band signalling. Same problem DTMF, SS5, etc. had. I would have expected the issue to be intuitvely obvious to anyone who's heard of a blue box?

(LLMs are unreliable oracles. They don't need to be fixed, they need their outputs tested against reality. Call it "don't trust, verify").